Rotary vane vacuum pump with filter means for inlet

ABSTRACT

An improved design of a rotary vane-type vacuum pump which prevents the oil used to lubricate the moving parts of the pump from entering the intake line of a connected vacuum chamber. The improvement comprises forming the inlet port in the front face of the cover plate which seals the end of the rotor casing. Filters are positioned in the intake port to catch any oil flowing along the inner wall of the intake port and to condense any oil foam entering therein. In order to facilitate the condensing of the oil foam, the inlet port is divided into two connected chambers, the lower of said chambers being of sufficient capacity to collect said oil foam flowing from the pump during its operation. A check valve is also positioned in the inlet port ahead of said filters in order to prevent the vacuum pressure in the vacuum chamber and intake line from dissipating through the pump and oil mist being drawn into the intake port when the pump is stopped.

INTRODUCTION

The present invention relates generally to a rotary vane-type vacuumpump and, more particularly, to an improved design thereof whichprevents the oil used to lubricate the moving parts of the pump fromentering the intake line of a connected vacuum chamber.

BACKGROUND OF THE INVENTION

In older vane-type vacuum pumps, the rotor and vanes were generally madeof steel. However, since such construction resulted in the rotor andvanes being relatively heavy, strong centrifugal forces were createdduring the operation of the pump which shortened the service life of thedevice. For this reason, manufacturers have more recently begun makingthe rotors of sintered metals. Such rotors are advantageous for bothproduction and cost reasons. Furthermore, such rotors are very strongwhile being both light weight and wear resistant.

However, since oil is used to lubricate the moving parts of the pump,the introduction of sintered metal as the rotor material has resulted adisadvantage that substantially more oil can be absorbed in its poresthan with steel. Therefore, at high rotational speeds, substantiallymore oil will be spun out of the rotor pores and be deposited againstthe walls of the rotor casing.

Since production techniques have usually required that the inlet openingof the pump extend radially outward through the casing, the separatedoil would be thrown into this suction inlet opening. This oil would bedeposited on the walls of the inlet opening and creep along them towardthe vacuum chamber in spite of the opposed suction effect. Such oil flowhas been found to be especially damaging to vacuum systems such as brakeenergizers since such systems generally have a diaphragm wall which issusceptable to being attacked by the oil, thereby rendering the entirebrake energizer system inoperable.

BRIEF DESCRIPTION OF THE INVENTION

The present invention generally avoids the above-discussed problems byallowing the rotor of a vane-type vacuum pump to be made of a sinteredmaterial without any danger that oil will be permitted to flow into theintake line of a connected vacuum chamber such as a brake energizer.

The present invention advantageously accomplishes this result by formingthe inlet port in the front face of the cover plate which seals therotor casing at its axial end. As a result of this design, oil can nolonger be directly thrown into the inlet port.

Furthermore, in order to prevent the vacuum pressure in the vacuumchamber and intake line from dissipating through the pump and oil mistbeing drawn into the intake port if the pump suddenly stops, a checkvalve may be positioned in the inlet port. This particular embodiment ofthe present invention offers the further advantage of permitting thebrake energizer of a motor vehicle to become fully functional as soon asthe engine is started again after it has been briefly stopped in thatthe pump is not again required to evacuate the vacuum chamber.

Even if it is not necessary that the vacuum pressure be maintained afterthe pump is turned off, it is important that any resulting reverse aircurrent not deliver oil to the intake line or vacuum chamber. Hence,another embodiment of the present invention proposes placing a filter inthe inlet port to prevent this occurrence.

If oil foam also appears in the system, a filter which acts as acondensation plate may be placed at the point connecting two chambers ofthe inlet port which have differing capacities in order to separate theoil from the oil foam. For this reason, it is advantageous to constructboth the filter and the chamber below it out of metal.

Since it is not possible for such a filter element to hold back any oilflowing along the walls of the inlet port, a further embodiment of thepresent invention provides for a second, cup-shaped suspension mountedfilter to be positioned, in an intake direction, in the chamber ahead ofthe other connected chamber. In order to facilitate the dripping of oiloff of this filter, it is preferably that its drip nose contacts thefirst filter.

In order to ensure a safe transporting of a bigger quantity of oil, itis suggested that the drip nose is centrically penetrating the firstfilter. By doing so, the course of the drop is no longer interrupted.

In order that for this arrangement the oil drops can be forwarded in abetter way, the second filter is arranged non-porously within the rangeof the drip nose, which is equipped with a bore inside. Thus, anenlarged suction force is acting onto the drops on the inner wall of thefilter. Furtheron it is avoided that--when stopping the pump--, oil isremaining within the filter and is creeping along the inner wall of theinlet port in direction to the vacuum chamber.

In order to facilitate the erection of the filters in the inlet port, itis recommended to arrange said filters in a bushing. The completelypre-erected bushing then will be installed into the inlet port.Moreover, it is advantageous that both, bushing and second filter areforming one unit and should be manufactured of plastic material, becausethe second filter is acting as a barrier for the oil, which is creepingalong the inner wall of the inlet port. It is recommended to use anon-wetting plastic material.

Locating the check valve ahead, in an intake direction, of said secondfilter ensures in a simple manner that oil cannot enter the vacuumchamber and that the vacuum pressure in the chamber will not dissipateif there is an interruption in the operation of the vacuum pump. Withthe present invention it is possible to use very simply constructedcheck valves whose sealing effect is based only upon the elasticity of arubber ring which opens or closes the openings in an orifice plate inresponse to the vacuum pressure. The use of such simple check valves inthe inlet port have not been possible before the present invention dueto the fact that oil deposited on the rubber ring caused it to stick tothe orifice plate thereby not allowing it to open either when the thepump was operated or when there was a vacuum present on the pump inletside of the system.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross-sectional view of a rotary vane-type vacuum pumpconstructed in accordance with an embodiment of the present inventionwith the rotor cross-sectional portion being taken along lines I--I ofFIG. 2;

FIG. 2 is an end cross-sectional view of a portion of the apparatusshown in FIG. 1;

FIG. 3 is a partial side cross-sectional view of a rotary vane-type pumpconstructed in accordance with an alternate embodiment of the presentinvention; and

FIG. 4 is an alternate embodiment of the partial side cross-sectionalview of the pump, shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 illustrate an embodiment of a rotary vane-type vacuum pumpconstructed in accordance with the present invention. In general, thepump consists of a rotor casing 1, drive shaft 2, a plurality of vanes 3which are axially fulcrummed at rotor 4, and an end cover plate 5.

In operation, the pump evacuates a vacuum chamber, such as a brakeenergizer, through inlet port 6 which is formed in the front face ofcover plate 5. The pump outlet port which is preferably displaced byapproximately 180 degress from the inlet port may also be located incover plate 5 as is illustrated in phantom lines in the embodiment shownin FIG. 3 or it may lead radially outward from casing 1. A check valve 8is mounted in the intake port 6 ahead of filter 9 in intake direction 7.

As oil creeps upward along the walls of inlet port 6 during operation ofthe pump, it is stripped off the inner wall of the inlet port at filter9. Due to gravity and suction effects, the oil will flow along the outersurface of the filter to its drip nose 10. When the oil drop becomessufficiently large, it will be drawn away from this point by the suctionaction of the pump. Due to the fact that check valve 8 is not moistenedby the oil, it will not lose its operability during the life of thepump.

The pump illustrated in FIG. 3 has an inlet port 6 of a differingarrangement. The inlet port is divided into two connected chambers 12and 13 of differing capacities. Lower chamber 12 is separated from upperchamber 13 by filter 11 which has a cross-sectional area ofsubstantially the same size as the cross-sectional area of the chambers.Filter 11 and chamber 12 have the function of catching the oil foamdrawn from the pump casing and, hence, are preferably made of metal. Thesize of chamber 12 corresponds to the amount of oil foam expected to bedrawn from the pump casing. The oil foam will condense on filter 11 andbe channeled back into the pump.

A second cup-shaped filter 9 is suspension mounted in chamber 13 aheadof filter 11 in intake direction 7. Filter 9 serves to divert any oilflowing out of chamber 12 along the inner wall of the inlet port awayfrom check valve 8 so that it and the remainder of the intake line willremain free of oil. For this reason, both filter 9 and chamber 13 arepreferably made of a non-wetting material such as plastic. Theconnection of filters 9 and 11 by drip nose 10 facilitates the drippingoff of the oil collected by filter 9. FIG. 4 shows an alternatearrangement of the two filters 9 and 11 in the intake port 6. Here, thechamber 13 is limited by the plastic bushing 17, to which bushing thesecond filter 9 is mounted. The plastic bushing 17 is fitted in chamber12, which has a greater diameter than the chamber 13.

The second filter 9 shows a cylindrical shape. At its lower part, seenin intake direction, the filter 9 shows a marked drip nose 14. Withinthe range of the drip nose 14, the filter 9 is layed out non porously,i.e. a small tank 15 is formed. The flow-off of this tank 15 is built bya centrical bore.

The drip nose penetrates the first filter 11, which filter is formed asa convex ball segment and is arranged in front of bushing 17. Because ofthe shape of the filter, also in this case the oil flows down at thefilter. Based on the suction force of the pump, the oil isre-transported either through bore 16 or along the outer wall of thefilter 9 via filter 11.

The pump as shown in FIG. 4 functions in the same way as shown in FIG. 1respectively FIG. 3.

While several particular embodiments of the present invention have beenshown and described in detail, it should be understood that variousobvious changes and modifications thereto may be made, and it istherefore intended in the following claims to include all suchmodifications and changes as may fall within the spirit and scope ofthis invention.

What is claimed is:
 1. In a rotary vane-type vacuum pump having a drivenrotor element with vanes mounted thereon located within a casing whichis sealed at one end by a cover plate, wherein the improvementcomprises:an inlet port formed in the front face of said cover platewhich is divided into upper and lower connected chambers of differingcapacities, a first filter located at the connecting point between saidchambers and extending across the cross-sectional area thereof, a secondcup-shaped filter suspension mounted in said upper chamber which islocated, in an intake direction, ahead of said lower chamber, and acheck valve located in said upper chamber.
 2. The vacuum pump of claim 1wherein said second filter has a drip nose which contacts said firstfilter.
 3. The vacuum pump of claim 2 wherein said drip nose iscentrically penetrating the first filter via a bore.
 4. The vacuum pumpof claim 3 wherein in the area of said drip nose the second filter islayed out non-porously and shows an axially extended bore within saiddrip nose.
 5. The vacuum pump of claim 4 wherein said two filters arearranged in a bushing, said bushing being adapted to the inlet port andforming said upper chamber which is located, in an intake direction,ahead of said lower chamber.
 6. The vacuum pump of claim 5 wherein thesecond filter and said bushing form one unit and are manufactured ofplastic material.
 7. The vacuum pump of claim 6 wherein said check valveis located, in an intake direction, ahead of said second filter.